I remember those days, and I remember those chess computers

I remember wanting the Mephisto with the wooden chess board so bad, I could taste it, as a kid
It sounds like you were an excellent chess player. I think you are part right in that, it would be quite difficult to re-memorize all the opening lines to the 8-10th move. That having been said, someone who was as advanced in chess as you were, should be able to once again become a very strong player from a tactical and strategic standpoint.
What I did for about 2 years was assign specific study times to chess. I did most of this during Covid. I would sit down for 3-4 hours, 3x a week and purely focus on chess. I also bought Polgar's "Chess; 5334 Problems, Combinations and Games". It is very good indeed. I have read many chess books, only this one and Nunn's stand out.
What you learned as a child is still all preserved in your brain, you just forgot how to access the information.
I urge you to take up your old hobby again. You seem to really miss it.